1. Field of the Invention
The present invention generally relates to graphics processing and more specifically to alpha-to-coverage using virtual samples.
2. Description of the Related Art
Anti-aliasing techniques that increase the sampling rate are used to improve the quality of images produced from rendered three-dimensional graphics primitives. Multiple sample locations are specified for each pixel and the sample coverage of the graphics primitives is represented by a per-pixel coverage mask that includes a bit for each one of the multiple samples. The coverage mask is used to determine the contribution of the graphics primitive to the final color for the pixel.
When a graphics primitive is texture mapped using a texture map that includes an alpha value that specifies transparency, the conventional approach is to blend the color of the foreground pixel with the background color in proportion to the alpha value. This requires sorting primitives in back-to-front or front-to-back order, which may be expensive or impractical.
Accordingly, what is needed in the art is a system and method for determining high resolution coverage masks that represent textured transparency when anti-aliasing is enabled.